Zoom type projection lens system having three movable members and a finite focus



Oct 1970 R. M. ALTMAN m m- 3,533,678

ZOOM TYPE PROJECTION LENS SYSTEM HAVING THREE MOVABLE MEMBERS AND A FINITE FOCUS Filed April 5, 1969 AXIAL RAY l4 s L v m APERT.

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5'8 FIG. RICHARD M. ALTMAN LYNN L. VAN ORDEN INVENTOR8 ATTORNEY United States Patent 0 ZOOM TYPE PROJECTION LENS SYSTEM HAVING THREE MOVABLE MEMBERS AND A FINITE FOCUS Richard M. Altman, Beverly Hills, Calif., and Lynn L. Van Orden, Holley, N.Y., assignors to Bausch & Lomb Incorporated, Rochester, N.Y., a corporation of New York Continuation-impart of application Ser. No. 621,960,

Mar. 9, 1967. This application Apr. 3, 1969, Ser. No. 820,696

Int. Cl. G02b 15/14 US. Cl. 350-184 9 Claims ABSTRACT OF THE DISCLOSURE A projection lens system having three movable lens members, the focal length thereof being continuously variable ovcr a magnification range or substantially 6 and working at finite conjugates.

REFERENCE TO RELATED PATENT APPLICATIONS This application is a continuation in part of our copending application now abandoned, Ser. No. 621,960, filed Mar. 9, 1967.

BACKGROUND OF THE INVENTION The present invention is related to projection lens systems of complex nature which work at fixed conjugates, and more particularly it relates to a zoom type of projection lens system having a variable equivalent focal length lying within a magnification range of substantially 6.

Such a projection lens system is used typically in projecting an image of a small film surface onto a nearby screen, so as to fill the screen regardless of the magnification used. Other kindred uses of the present invention are contemplated such as its use as a component of a projection microscope.

Zoom projection lens systems of the general kind above described are exemplified by British 17,842/97 issued to Society, Mar. 19, 1897; Mellor 2,159,394 issued May 23, 1939; and Peck et a1. 3,185,029 issued May 25, 1965, none of which show the optical form of the projection lens system to be described hereinafter.

SUMMARY OF THE INVENTION The present invention is directed particularly toward the form and arrangement and construction of the lens elements which constitute the lens system and accordingly it is an object of said invention to provide a relatively low power zoom lens system composed of three moving lens groups which are so differentially moved relatively to a fixed point on the axis thereof that the magnification of the system is varied over 'a range of magnification of substantially 6 while high grade imagery is preserved throughout.

It is a further object to provide such a device which projects an image of an object surface and at continuously variable magnification but constant screen brightness, the optical constructional data related to the aforesaid projection lens system being so chosen that the chromatic and monochromatic lens aberrations as well as distortion are well corrected for high grade imaging performance throughout the entire range of magnification; particularly regarding reduced secondary color.

Further objects and advantages will be apparent to those skilled in the art by reference to the following specification taken in connection with the accompanying drawing wherein;

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FIG. 1 is an optical diagram showing a preferred form of the present invention in one operational position, and

FIG. 2 is similar to FIG. 1 except that a second operational position of the invention is shown.

Said preferred form of the invention comprises a zoom lens system which is generally designated by numeral 10 and which works at fixed conjugates between a fixed object surface 0 and a fixed image surface designated 18. In the preferred form of the invention, the object surface 0 represents a photographic film surface having 2%" x 2%" format size, and an image of said film is formed on an image surface 18 which is a screen 11%" x 11%".

By means of the zoom lens system 10, the magnification of the image formed on screen 18 is varied between substantially 5x and 30X through a magnification range of substantially 6 while keeping the size of the image on the screen as well as the screen illumination constant.

This means that only at 5 magnification is the entire format size of the film viewed on the screen. In other words, the numerical aperture of the lens system 10 on the image'side remains constant. At increased magnifications, the state of correction of the image aberrations remains excellent.

Comprised in said zoom lens system 10 is a first movable lens group 11 which is optically aligned on an optical axis 19 with a second movable lens group 12, and a third movable lens group 13 on one side of the aperture stop 14 of the lens system 10.

Optically aligned along the axis 19 with the lens groups 11, 12, and 13 on the other side of the aperture stop 14 is a fixed group of lenses 15 which focuses the image rays, one of which is shown at 20, at the fixed image plane 18.

Said first movable lens group 11 comprises a front positive singlet meniscus lens member designated I which is located at a variable axial distance S from the object 0. Next rearwardly from lens member I is a double convex doublet lens member II which is spaced at a fixed distance S from member I. Preferably lens member II is comprised of a front double convex lens element IIa which lies in contact with a rear concavo-convex lens element 11b of meniscus form.

In edge contact with the rear surface of lens element IIb lies a double concave lens member III, the confronting radii thereof being such that an airspace S is provided therebetween. Rearwardly of lens member III at an axial distance 8, therefrom is mounted a double convex lens member IV, and mounted rearwardly of member IV is another double convex lens member V which is spaced therefrom at an axial distance S Next comprised in lens group 11 is a double concave lens member VI spaced at an axial distance S from lens member V and mounted in edge contact on its rear surface is still another double convex lens member VII, the axial airspace S between members VI and VII being in the shape of a positive meniscus.

Located rearmost in the first movable lens group 11 is a positive meniscus singlet lens member VIII at an axial distance 8,, from member VII, the concave side thereof facing rearwardly.

Comprised in the second movable lens group 12 is a front double concave lens member IX which is separated from the first lens group 11 by a variable axial airspace S Lying in edge contact with the rear surface of member IX is a doublet lens member X which is composed I of a front double concave lens element Xa and a contiguous rear double convex lens element Xb. The axial airspace between members IX and X is designated S The rearmost and third movable lens group 13 is separated from the second movable lens group 12 by a variable airspace S Included in said third group 13 is a front double convex lens element XI and a rear Rearwardly of lens group 16 at a fixed axial distance S is provided the rearmost lens group 17 which is composed of a front concave-convex lens member XV and a rear double concave lens member XVI, the last two lens members being separated from each other by an axial airspace S Lens member XVI is spaced ahead of the image plane 18 at an axial distance of S Having described hereabove the basic form of the novel zoom lens system 10, the optical constructional data which has been found to be successful in fulfilling the stated objects in a preferred form of the present invention are given herebelow.

Ideally the values for the equivalent focal lengths of the first movable lens group 11, second movable lens group 12 and third movable lens group 13 are respectively substantially 2.19 L -1.10 L and 8.16 L wherein L represents one tenth of the axial distance between the aperture stop 14 and the object surface 0. Furthermore, the ideal values for the equivalent focal lengths of the front fixed lens member 16 and rear fixed lens member 17 are respectively 2.926 L and 1.618 L As the result of calculation and experiment, the ranges of values for the equivalent focal lengths F; to F of the aforementioned lens member I to XVI are given in terms of L in Table I herebelow wherein the minus sign denotes negative focal length, the ranges of values for the successive airspaces S to S in said system 10 being further given in said table along with the ranges of values for the successive axial lens thicknesses t to r of the lens elements in lens groups 11, 12 and 13.

- Table I With regard to Table I, it will be seen that the value of each lens parameter is given in the form of a range of values which include a nominal or ideal value. All of said ranges are so stated for the primary purpose of paralleling the practices used in manufacturing the lens elements.

It is well known in the lens making art that it is practically impossible to manufacture a production run of lens elements economically while holding all of the lens parameters to specific and ideal values. Therefore, the lens designer specifies tolerances or ranges of values for each lens parameter Within which the lens parts may be manufactured economically while nevertheless permitting the production of a completed objective which is capable of good optical performance.

The technique used by the manufacturer is to separate out the lens elements which fall within the established ranges of values and under the supervision of skilled Opticians selectively assemble from these elements a complete objective 10. This technique is highly successful in producing economically a good lens system having an optical performance suited to its use.

In Table II herebelow, the absolute values in ranges for the refractive indices u (I) to m; (XII) as well as the absolute values in ranges for the Abbe 11 number of the successive lens elements I to XII are given,

TABLE II Furthermore values in ranges and in terms of L are given in Table III herebelow for the successive radii of the lens surfaces --R to R on the lens elements I to XII, the minus sign designating those surfaces which have their centers of curvature on the object sid of that surface.

TABLE III 6.5535 L R 6.6875 L 1.9271 L -R 1.9659 L 9.1416 L R 9.3262 L 1.6855 L -R 1.7195 L 4.1725 L R 4.2587 L 2.8119 L R 2.8687 L 4.7976 L R 4.8944 L 3.8639 L R 3.9419 L 2.8849 L R 2.9421 L 8.9637 L R 9.1447 L 5.8273 L -R 5.9449 L 6.0200 L -R 6.1416 L 2.6609 L R 2.7145 L 3.0271 L R 3.0881 L 8.4777 L R 8.6489 L 2.5318 L R 2.5828 L 24.7183 L R 2s.2175 L 1.1648 L -R 1.1882 L 1.1183 L R 1.1407 L 2.6114 L R 2.6640 L .6074 L R .6196 L 5.3860 L R 5.4948 L 16.7893 L R 17.1283 1.

1.5339 L R 1.5699 L 1.5361 L R 1.5671 L 3.9379 L -R 4.0204 L It will be understood that the parts of the total lens system 10, which are dimensionally and otherwise specified in Tables I, II and III, constitute the zooming members, and said parts may be combined with a fixed lens assembly 15 of different optical form than that which is shown and described herein under the condition that the fixed lenses together with the movable lenses form an image on the screen surface lying at 18. Therefore, the illustrated and described fixed lens portion 15 may be conplane 18.

TABLE IV In Table V given herebelow, the aforementioned nominal or ideal values for all of the constructional parameters found in the previous four tables is given substantially in terms of L except the values for the refractive index 11 and Abbe number '1' which have absolute values.

When the constructional parameters have substantially the values given in Table V the values for the focal lengths F(IIa) m .o9 substantially Also, the values for the focal lengths F(Xa) and F(Xb) have a numerical relationship as stated herebelow.

F(Xa) FtXb) Although only a preferred form of the present invention is shown and described in detail, other forms are possible and changes may be made in the specific values of the constructional data herein set forth within the ranges of values stated without departing from the spirit of the invention.

We claim:

1. A zoom type of projection lens system which includes three difierentially movable lens members which are moved between fixed object and image position according to such a law that the magnification of the image formed is constant in border size although it is varied in magnification through a continuous magnification range of substantially 6, said image being well corrected and substantially stationary, said system including a first axially, movable lens group which is spaced from said object surface at a variable axial distance designated S a second axially movable lens group which is spaced 1.09 substantially from said first group at a variable axial distance designated S and a third axially movable lens group which is spaced from said second group at a variable axial distance designated S said groups being optically aligned on one side of the aperture stop of said system on the opposite side from at least one fixed projection lens group which forms said image at a fixed position,

said first movable lens group comprising a front singlet meniscus lens member designated I which is concave toward said object surface,

a double convex doublet lens member designated II which is spaced rearwardly of member I at a fixed axial distance designated S a double concave lens member designated III which has a front surface of short curvature so that it lies in edge contact with lens member II,

a double convex lens member designated IV which is spaced at a fixed axial distance designated 8.; from member III,

another double convex lens member designated V which is spaced at a fixed axial distance designated S from member IV,

a second double concave lens member designated VI which is spaced at a fixed axial distance designated S; from member V,

a third double convex lens member designated VII which has a refracting surface which is flatter than the adjacent surface of member VI and has edge contact therewith, and

a rearmost singlet meniscus lens member designated VIII which is concave toward said images and is spaced at a fixed axial distance designated S from member VII,

said second movable lens group comprising a front double concave singlet lens member designated IX and a positive meniscus doublet lens member designated X which is concave toward and lies in edge contact with member IX,

and third movable lens group comprising a front double convex lens member designated XI and,

a rear meniscus lens member designated XII which is concave toward member XI and is spaced therefrom at a fixed axial distance designed S the variable airspace between member XII and said aperture stop being designated S the values for the focal lngths F(I) to F(XII) of the successive lens members I to XlI respectively being substantially as given in the table herebelow in terms of L; which represents .1 of the axial length from said object surface to said aperture stop, the minus sign meaning negative focal length and the successive airspaces S to S in said system having values in terms of L as given in said table,

5.247 L F(I) 5.353 L 6.967 L F(II) 7.107 L 2.863 L F(III) 2.921 L 3.261 L :F(IV) 3.327 L 6.905 L -F(V) 7.045 L 2.987 L F(VI) 3.048 L 4.369 L F(VII) 4.457 L 5.473 L F(VIII) 5.584 L 0.922 L -F(IX) 0.941 L 7.454 L F(X) 7.604 L 2.747 L F(XI) 2.802 L 4.159 L -F(XII) 4.243 L 2.1689 L S 2.2128 L (5x) 5.2336 L S 5.3393 L 9x) 3.8408 L S 3.9184 L (16.5x) 2.9006 L S 2.9592 L (30X) .0140 L S .0143 L .0179 L S .0l82 L .0140 L S .0143 L S .0069 L .0140 L S .0143 L .1528 L S .1559 L (5X) .6723 L S .6858 L (9X) 1.5411 L S l.5722 L (16.5 2.7364 L S 2.7917 L (30X) .6897 L S .7036 L (5X) 1.1869 L S 1.2109 L (9X) 0.457 L S .0467 L (16.5 .2518 L S .2569 L (BOX) .0279 L S .0285 L 4.3318 L S 4.4193 L (5X) .2505 L S .2556 L (9X) 1.5040 L S 1.5344 L (l6.5 1.4544 L S 1.4838 L (30X) 2. A zoom type of projection lens system which includes I three differentially movable lens members which are moved between fixed object and image positions according to such a law that the magnification of the image formed is constant in border size although it is varied in magnification through a continuous magnification range of substantially 6, said mage being well corrected and substantially stationary, said system including a first axially movable lens group which is spaced from.

said object surface at a variable axial distance designated S a second axially movable lens group which is spaced from said first group at a variable axial distance designated S and a third axially movable lens group which is spaced from said second group at a variable axial distance designated S said groups being optically aligned on one side of the aperture stop of said system on the opposite side from at least one fixed projection lens group which forms said image at a fixed position, Said first movable lens group comprising a front singlet meniscus lens member designated I which is concave toward said object surface,

a double convex doublet lens member designated II which is spaced rearwardly of member I at a fixed axial distance designated 5;,

a double concave lens member designated III which has a front surface of short curvature so that it lies in edge contact with lens member II,

a double convex lens member designated IV which is spaced at a fixed axial distance designated 5., from member III,

another double convex lens member designated V which is spaced at a fixed axial distance designated S from member IV,

a second double concave lens member designated VI which is spaced at a fixed axial distance designated 8,; from member V,

a third double convex lens member designated VII which has a refracting surface which is flatter than the adjacent Surface of member VI and has edge contact therewith, and

a rearmost singlet meniscus lens member designated VIII which is concave toward said images and is spaced at a fixed axial distance designated S from member VII,

said second movable lens group comprising a front double concave singlet lens member designated IX and a positive meniscus doublet lens member designated X which is concave toward and lies in edge contact with member IX,

said third movable lens groups comprising a front double convex lensmember designated XI and,

a rear meniscus lens member designated XII which is concave toward member XI and is spaced therefrom at a fixed axial distance designated 8, the variable airspace between member XII and said aperture stop being designated S,;,,

the values for the focal lengths F(I) to F(XII) of the successive lens members I to XH respectively being substantially as given in the table herebelow in terms of L, which represents .1 of the axial length from said object surface to said aperture stop, the minus sign meaning negative focal length, the values furthermore being given in terms of L, substantially for' the successive airspaces S, to S the successive axial thicknesses t, to 1,, of the aforesaid lens members, t and t being related to the positive and negative lens elements respectively in member II, and t,, and t, being related to the negative and positive lens elements respectively in member X, the corresponding values for the refractive index n and Abbe number 1/ being given herebelow in absolute values for the successlve lens parts,

3. A zoom type of projection lens system which includes three differentially movable lens members which are moved between fixed object and image positions according to such a law that the magnification of the image formed is constant in border size although it is varied in magnification through a continuous magnification range of substantially 6, said image being well corrected and substantially stationary, said system including a first axially movable lens group which is spaced from said object surface at a variable axial distance designated S a second axially movable lens group which is spaced from said first group at a variable axial distance designated S and a third axially movable lens group which is spaced from said second group at a variable axial distance designated S said groups being optically aligned on one side of the aperture stop of said system on the opposite side from at least one fixed projection lens group which forms said image at a fixed position,-

said first movable lens group comprising a front singlet meniscus lens member designated I which is concave toward said object surface,

a double convex doublet lens member designated II which is spaced rearwardly of member I at a fixed axial distance designated S a double concave lens member designated III which has a front surface of short curvature so that it lies in edge contactwith lens member H,

a double convex lens member designated IV which is spaced at a fixed axial distance designated S; from member III,

another double convex lens member designated V which is spaced at a fixed axial distance designated S from member IV,

a second double concave lens member designated VI which is spaced at a fixed axial distance designated S from member V,

a third double convex lens member designated VII which has a refracting surface which is flatter than the adjacent surface of member VI and has edge contact therewith, and

a rearmost singlet meniscus lens member designated VIII which is concave toward said image and is spaced at a fixed axial distance designated 5;, from member VII,

said second movable lens group comprising a front double concave singlet lens member designated D( and a positive meniscus doublet lens member designated X which is concave toward and lies in edge contact with member IX,

said third movable lens group comprising a front double convex lens member designated XI, and

a rear meniscus lens member designated XII which is concave toward member XI and is spaced therefrom at a fixed axial distance designated S the variable airspace between member XII and said aperture stop being designated S 1 the values for the radii wlich are designated R to R respectively for the successive lens members I to XII being given in terms of L which represents one tenth of the axial length between the object plane and the aperture stop of said system, the minus sign being used for those lens surfaces whose centers of curvature lie on the front side of the respective surfaces, the values furthermore being given in terms of L for the successive airspaces designated S to S the values of the successive axial thicknesses of lens members I to XII which are designated t to i being given in the table in terms of L along with the absolute values of refractive index n and Abbe number 1 for the aforesaid lenses,

6.5535 L -R 6.6857 L 1.9271 L R 1.9659 L 9.1416 L R 9.3262 L 1.6855 L -R 1.7195 L 4.1725 L R 4.2587 L 2.8119 L R 2.8687 L 4.7976 L1 R7 4.8944 L 3.8639 L R 3.9419 L 2.8849 L R 2.9421 L 8.9637 L R 9.1447 L 5.8273 L --R 5.9449 L 6.0200 L R 6.1416 L 2.6609L R 2.7145 L 3.0271 L R 3.0881 L 8.4777 L R15 8.6489 L 2.5318 L R 2.5828 L 24.7183 L R 25.2175 L 1.1648 L R1a 1.1822 L 1.1183 L R 1.1407 L 2.6114 L R 2.6640 L .6074 L R21 .'6196 L 5.3860 L R 5.4948 L 16.7893 L R '17.1283 L 1.5389 L 24 1.5699 L 1.5361 L R 1.5671 L 3.9379 L -R 4.0203 L .1676 L t .1709 L .3631 L t .3704 L .1676 L t .1709 L .1955 L t .1994 L .2933 L t .2992 L .1955 L t .1994 L .1676 L1 t7 .1709 L .2374 L t .2422 L .1676 L t .1709 L .0559 L t .0570 L .0559 L t .0570 L .1326 L t .1353 L .0768 L t .0784 L 4. A zoom type of projection lens system which includes three differentially movable lens members which are moved between fixed object and image positions according to such a law that the magnification of the image formed is constant in border size although it is varied in magnification through a continuous magnification range of substantially 6, said image being well corrected and substantially stationary, said system including a first axially movable lens group which is spaced from said object surface at a variable axial distance designated S a second axially movable lens group which is spaced from said first group at a variable axial distance designated S and a third axially movable lens group which is spaced from said second group at a variable axial distance designated S said groups being optically aligned on one side of the aperture stop of said system on the opposite side from at least one fixed projection lens group which forms said image at a fixed position,

.said first movable lens group comprising a front singlet meniscus lens member designated I which is concave toward said object surface,

a double convex doublet lens member designated II which is spaced rearwardly of member I at a fixed axial distance designated S a double concave lens member designated III which has a front surface of short curvature so that it lies in edge contact with lens member II,

a double convex lens member designated IV whichis spaced at a fixed axial distance designated S from member III,

another double convex lens member designated V which is spaced at a fixed axial distance designated S from member IV,

a second double concave lens member designated VI which is spaced at a fixed axial distance designated S from member V,

a third double convex lens member designated VII which has a refracting surface which is flatter than the adjacent surface of member VI and has edge contact therewith, and

a rearmost singlet meniscus lens member designated VIII which is concave toward said images and is spaced at a fixed axial distance designated S from member VII,

said second movable lens group comprising a front double concave singlet lens member designated IX and a positive meniscus doublet lens member designated X which is concave toward and lies in edge contact with member IX,

said third movable lens group comprising a front double convex lens member designated XI and,

a rear meniscus lens member designated XII which is concave toward member XI and is spaced therefrom at a fixed axial distance designated S the variable airspace between member XII and said aperture stop being designated S the values for the focal lengths F(I) to F(XII) of the successive lens members I to XII respectively Sa=2.7640 L1 (30X) 5. A zoom type of projection lens system which ina rearmost singlet meniscus lens member designated VIII which is concave toward said images and is spaced at a fixed axial distance designated S from member VII,

said second movable lens group comprising a front double concave singlet lens member designated IX and a positive meniscus doublet lens member designated X which is concave toward and lies in edge contact with membef IX,

said third movable lens group comprising a front double convex lens member designated XI and,

a rear meniscus lens member designated XII which is concave toward member XI and is spaced therefrom at a fixed axial distance designated S the variable airspace between member XII and said aperture stop being designated S the values for the focal lengths F(I) to F(XII) of the successive lens members I to XII respectively being substantially as given in the table herebelow in terms of L, which represents .1 of the axial length from said object surface to said aperture stop, the minus sign meaning negative focal length and the successive airspaces S to S in said system having values substantially as given in the table herebelow in terms of L as well as the substantial values of the lens thicknesses t to t of the successive lens elements, numbered from lens I to lens XII, the specific absolute values for the refractive index n and Abbe number n for the successive lens elements of the lens members I to XII being given substantially in the table herebelow,

cludes three differentially movable lens members which are moved between fixed object and image positions according to such a law that the magnification of the image formed is constant in border size although it is varied in 40 magnification through a continuous magnification range of substantially 6, said image being well corrected and substantially stationary, said system including a first axially movable lens group which is spaced from u (II pos.) =1.514 nn (H neg.)=1.613 up (III) =1.613

m (IV)=1.514

said object surface at a variable axial distance designated S a second axially movable lens group which is spaced from said first group at a variable axial distance designated S and a third axially movable lens group which is spaced a front singlet meniscus lens member designated I which is concave toward said object surface,

a double convex doublet lens member designated II which is spaced rearwardly of member I at a fixed axial distance designated S a double concave lens member designated III which has a front surface of short curvature so that it lies in edge contact with lens member II,

a double convex lens member designated IV which is spaced at a fixed axial distance designated 5,, from member III,

another double convex lens member designated V which is spaced at a fixed axial distance designated S from member IV,

a second double concave lens member designated VI which is spaced at a fixed axial distance designated S; from member V,

a third double convex lens member designated VII which has a refracting surface which is flatter than m (X pos.) =1.751

no (XI)=1.514

. II (II pos.)=70.2

II (II neg.) =44.2

I (III) =44.2

u (IV)=70.2

u (VI)=44 2 v (VII) =70 2 11 (VIII) =70 2 v (X neg.) =44 2 v (XII) =44.2

F (I)=5.300 Ll S1=2.l908 LI (5X) F (II)=7.037 L1 S1=5.2864 LI (9X) F (III)=2 891 L S =3.8795 L1 (16.5X) F (IV) =3.294 L1 S1=2.9299 L1 (30X) F (V)=6.975 L1 Sz=.014l 1 -F (VI)=3.018 LI S4=.018I L; F (VII) =4.413 Li S5=.014l. L; F (VIII)=5 529 Li Ss= 0071 L1 F (IX)=0 931 L1 S 0141 L; F (X)=7,529 LI So= 1543 L1 (5X) F (XI)= .774 L1 Sa= 6970 L1 (9X) -F (XII) =4.201 L1 Sa=l.5566 L1 (16.5X) t =.1692 L1 Sn=2.7640 L1 (30X) tg=.3667 L Sio= l 6. A zoom type of projection lens system which includes three differentially movable lens members which magnification through a continuous magnification range of substantially6, said image being well corrected and substantially stationary, said system including of refractive index 11 and Abbe number 11 for the aforesaid lenses, 1

a first axially movable lens group which is spaced from said object surface at a variable axial distance designated a second axially movable lens group which is spaced from said first group at a variable axial distance designated S and a third axially movable lens group which is spaced from said second group at a variable axial distance designated S said groups being optically aligned on one side of the aperture stop of said system on the opposite side from at least one fixed projection lens group which forms said image at a fixed position,

said first movable lens group comprising a front singlet meniscus lens member designated I which is concave toward said object surface,

a double convex doublet lens member designated II which is spaced rearwardly of member I at a fixed axial distance designated a double concave lens member designated III which has a front surface of short curvature so that it lies in edge contact with lens member II,

a double convex lens member designated IV which is spaced at a fixed axial distance designated S from member III,

another double convex lens member designated V which is spaced at a fixed axial distance designated S from member IV,

- a second double concave lens member designated VI which is spaced at a fixed axial distance designated. S from member V,

a third double convex lens member designated VII which has a refracting surface which is flatter than the adjacent surface of member VI and has edge contact therewith, and

a rearmost singlet meniscus lens member designated VIII which is concave toward said images and is spaced at a fixed axial distance designated from member VII,

said second movable lens group comprising a front double concave singlet lens member designated IX and a positive meniscus doublet lens member designated X which is concave toward and lies in edge contact with member IX,

said third movable lens group comprising a front double convex lens member designated XI and,

a rear meniscus lens member designated XII which is concave toward member XI and is spaced therefrom at a fixed axial distance designated S the variable airspace between member XII and said aperture stop being designated S the specific values for the radii which are designated R to R respectively for the successive lens members I to XII being given in terms of L which represents one-tenth of the axial length between the object plane and the aperture stop of said system, the minus sign being used for those lens surfaces whose centers of curvature lie on the front side of the respective surfaces, the values furthermore being given in terms of L for the successive airspaces designated S to S the specific values of the successive axial thicknesses of lens members I to XII which are designated t to being given in the table in terms of L along with the absolute values are moved between fixed object and image positions according to such a law that the magnification of the image formed is constant in border size although it is varied in magnification through a continuous magnification range of substantially 6, said image being well corrected and substantially stationary, said system including,

a first axially movable lens group which is spaced from said object surface at a variable axial distance designated S a second axially movable lens group which is spaced from said first group at a variable axial distance designated S I a third axially movable lens group which is spaced from said second group at a variable axial distance designated S said groups being optically aligned on the front side of the aperture stop of said system at a variable axial distance designated S from said stop, and

a stationary group of projection lenses comprising a front pair of lenses which include a front double convex lens element designated XIII which is located at a fixed axial distance designated S rearwardly from said aperture stop and is followed by a negative meniscus lens element designated XIV with an airspace S lying therebetween,

said stationary group further comprising a rear pair of lenses which include a front positive meniscus lens element designated XV which is concave toward the front and is spaced at a fixed distance S from element XIV, and further includes a rear double concave lens element designated XVI which is spaced from element XV by an airspace designated S said system forming a fixed image at a stationary plane which is located at an axial distance rearwardly therefrom designated 5,

said first movable lens group comprising a front singlet meniscus lens member designated I which is concave toward said object surface,

a double convex doublet lens member designated II which is spaced rearwardly of member I at a fixed axial distance designated S a double concave lens member designated III which has a front surface of short curvature so that it lies in edge contact with lens member II,

a double convex lens member designated IV which is spaced at a fixed axial distance designated 8., from member III,

another double convex lens member designated V which is spaced at a fixed axial distance designated S from member IV,

a second double concave lens member designated VI which is spaced at a fixed axial distance designated 8,, from member V,

a third double convex lens member designated VII which has a refracting surface which is flatter than the adjacent surface of member VI and has edge contact therewith, and

a rearmost singlet meniscus lens member designated VIII which is concave toward said images and is spaced at a fixed axial distance designated S from member VII,

said second movable lens group comprising a front double concave singlet lens member designated IX and a positive meniscus doublet lens member designated X which is concave toward and lies in edge contact with member IX,

said third movable lens group comprising a front double convex lens member designated XI and,

a rear meniscus lens member designated XII which is concave toward member XI and is spaced therefrom at a fixed axial distance designated S the variable airspace between member XII and said aperture stop being designated 8,

the values for the focal lengths F(I) to F(XVI) of the successive lens members I to XVI respectively being substantially as given in the table herebelow in terms of L, which represents .1 of the axial length from said object surface to said aperture stop, the minus sign meaning negative focal length, the values furthermore being given in terms of L, substantially for the successive airspaces S, to S 18: the successive axial thicknesses t, to t,., of the aforesaid lens members, 1 and t being related to the positive and negative lens elements respectively in member II, and t and r being related to the negative and positive lens elements respectively in member X, the corresponding values for the refractive index 71,; and Abbe number 7 being given for the successive lens parts herebelow in absolute values,

20 5.473 L, F(VIII) 5.584 L,

l.6ll n (III) 1.6145

l.5l30 n (IV) l.5150

l.6l n (VI) 1.6145

1.5l30 n (VII) 1.5l50

l.5130 n (VIII) l-.5150

1.6115 n (IX) 1.6145

1.6115 n (X neg.) l.6145

l.7490 rr (X pos.) 1.7510 l.5130 n (XI) 1.5150 l.6l15 n (XII) 1.6145

69.7 v (II pos.) 70.7

43.9 v (II neg.) 44.5

43.9 v (III) 44.5 69.7 v (IV) 70.7

69.7 11 (VII) 70.7 69.7 v (VIII) 70.7

43.9 v (IX) 44.5 43.9 1 (X neg.) 44.5

27.6 u (X pos.) 28.0 69.7(1 (XI) 70.7 43.9 v (XII) 44.5

8. A zoom type projection lens system as set forth in claim 1 further characterized by the equivalent focal length of said first movable lens group, said second movable lens group, and said third movable lens group being ideally 2.19 L 1.10 L and 8.15 L respectively.

9. A zoom type of projection lens system which includes three differentially movable lens members which are moved between fixed object and image positions according to such a law that the magnification of the image formed is constant in border size although it is varied in magnification through a continuous magnification range of substantially 6, said image being well corrected and substantially stationary, said system including a first axially movable lens group which'is spaced from said object surface at a variable axial distance designated S a second axially movable lens group which is spaced from said first group at a variable axial distance designated S and a third axially movable lens group which is spaced from said second group at a variable axial distance designated S11, said groups being optically aligned on one side of the aperture stop of said system on the opposite side from at least one fixed projection lens group which forms said image at a fixed position,

said first movable lens group comprising a front singlet meniscus lens member designated I which is concave toward said object surface,

a double convex doublet lens member designated II which is spaced rearwardly of member I at a fixed axial distance designated S member II being composed of a front double convex lens element IIa which lies in surface contact with a rear negative meniscus lens element IIb,

a double concave lens member designated III which has a front surface of short curvature so that it lies in edge contact with lens member II,

a double convex lens member designated IV which is spaced at a fixed axial distance designated 8.; from member III,

another double convex lens member designated V which is spaced at a fixed axial distance designated S from member IV,

a second double concave lens member designated VI which is spaced at a fixed axial distance designated from member V,

a third double convex lens member designated VII which has a refracting surface which is flatter than the adjacent surface of member VI and has edge contact therewith, and

a rearmost singlet meniscus lens member designated VIII which is concave toward said images and is spaced at a fixed axial distance designated S from member VII,

said second movable lens group comprising a front double concave singlet lens member designated IX and a positive meniscus doublet lens member designated X which is concave towardand lies in edge contact with member IX, member X being composed of a front double concave lens element Xa which lies in surface contact with a rear double convex lens element Xb,

said third movable lens group comprising a front double convex lens member designated XI and,

a rear meniscus lens member designated XII which is concave toward member XI and is spaced therefrom at a fixed axial distance designated S the variable airspace between member XII and said aperture stop being designated S the values for the focal lengths F(I) to F(XII) of the successive lens members I to XII and lens elements Ila, IIb, Xa and Xb respectively being substantially as given in the table herebelow in terms of L which represents .1 of the axial length from said object surface to said aperture stop, the minus sign meaning negative focal length and the successive airspaces S to S in said system having values in terms of L as given in said table,

Xb being related to each other numerically as stated herebelow,

F I 1 %:59 (numerically) 32:; 1.1 (numerically) 

